Check if page file valid before page display

app/src/main/kotlin/org/koitharu/kotatsu/core/util/ext/File.kt

@@ -26,6 +26,8 @@ fun File.takeIfReadable() = takeIf { it.exists() && it.canRead() }
 
 fun File.takeIfWriteable() = takeIf { it.exists() && it.canWrite() }
 
+fun File.isNotEmpty() = length() != 0L
+
 fun ZipFile.readText(entry: ZipEntry) = getInputStream(entry).bufferedReader().use {
 	it.readText()
 }

app/src/main/kotlin/org/koitharu/kotatsu/core/util/ext/Throwable.kt

@@ -87,3 +87,6 @@ fun Throwable.isWebViewUnavailable(): Boolean {
 	return (this is AndroidRuntimeException && message?.contains("WebView") == true) ||
 		cause?.isWebViewUnavailable() == true
 }
+
+@Suppress("FunctionName")
+fun NoSpaceLeftException() = IOException(MSG_NO_SPACE_LEFT)

app/src/main/kotlin/org/koitharu/kotatsu/local/data/PagesCache.kt

@@ -1,6 +1,7 @@
 package org.koitharu.kotatsu.local.data
 
 import android.content.Context
+import android.os.StatFs
 import com.tomclaw.cache.DiskLruCache
 import dagger.hilt.android.qualifiers.ApplicationContext
 import kotlinx.coroutines.Dispatchers
@@ -33,7 +34,8 @@ class PagesCache @Inject constructor(@ApplicationContext context: Context) {
 	}
 	private val lruCache = SuspendLazy {
 		val dir = cacheDir.get()
-		val size = FileSize.MEGABYTES.convert(200, FileSize.BYTES)
+		val availableSize = getAvailableSizeMb()
+		val size = SIZE_DEFAULT.coerceIn(SIZE_MIN, availableSize)
 		runCatchingCancellable {
 			DiskLruCache.create(dir, size)
 		}.recoverCatching { error ->
@@ -63,4 +65,20 @@ class PagesCache @Inject constructor(@ApplicationContext context: Context) {
 			file.delete()
 		}
 	}
+
+	private suspend fun getAvailableSizeMb(): Long = runCatchingCancellable {
+		val statFs = StatFs(cacheDir.get().absolutePath)
+		FileSize.BYTES.convert(statFs.availableBytes, FileSize.MEGABYTES)
+	}.onFailure {
+		it.printStackTraceDebug()
+	}.getOrDefault(SIZE_DEFAULT)
+
+	private companion object {
+
+		val SIZE_MIN
+			get() = FileSize.MEGABYTES.convert(20, FileSize.BYTES)
+
+		val SIZE_DEFAULT
+			get() = FileSize.MEGABYTES.convert(200, FileSize.BYTES)
+	}
 }

app/src/main/kotlin/org/koitharu/kotatsu/reader/domain/PageLoader.kt

@@ -12,6 +12,7 @@ import dagger.hilt.android.lifecycle.RetainedLifecycle
 import dagger.hilt.android.qualifiers.ApplicationContext
 import dagger.hilt.android.scopes.ActivityRetainedScoped
 import kotlinx.coroutines.CoroutineExceptionHandler
+import kotlinx.coroutines.Deferred
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.async
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -32,6 +33,7 @@ import org.koitharu.kotatsu.core.prefs.AppSettings
 import org.koitharu.kotatsu.core.util.FileSize
 import org.koitharu.kotatsu.core.util.RetainedLifecycleCoroutineScope
 import org.koitharu.kotatsu.core.util.ext.ensureSuccess
+import org.koitharu.kotatsu.core.util.ext.isNotEmpty
 import org.koitharu.kotatsu.core.util.ext.ramAvailable
 import org.koitharu.kotatsu.core.util.ext.withProgress
 import org.koitharu.kotatsu.core.util.progress.ProgressDeferred
@@ -103,7 +105,7 @@ class PageLoader @Inject constructor(
 	}
 
 	fun loadPageAsync(page: MangaPage, force: Boolean): ProgressDeferred<File, Float> {
-		var task = tasks[page.id]
+		var task = tasks[page.id]?.takeIf { it.isValid() }
 		if (force) {
 			task?.cancel()
 		} else if (task?.isCancelled == false) {
@@ -216,6 +218,15 @@ class PageLoader @Inject constructor(
 		return context.ramAvailable <= FileSize.MEGABYTES.convert(PREFETCH_MIN_RAM_MB, FileSize.BYTES)
 	}
 
+	private fun Deferred<File>.isValid(): Boolean {
+		return if (isCompleted) {
+			val file = getCompleted()
+			file.exists() && file.isNotEmpty()
+		} else {
+			true
+		}
+	}
+
 	private class InternalErrorHandler : AbstractCoroutineContextElement(CoroutineExceptionHandler),
 		CoroutineExceptionHandler {